In a saucepan, heat the butter, water, salt, and sugar. Once everything is melted, add all the flour at once and mix well with a wooden spoon.

Remove from heat. Add the eggs one at a time, mixing well after each addition until the dough is smooth.

Grease a baking sheet, then pipe small mounds of dough onto it using a piping bag.

Bake for 20 to 25 minutes at 400°F (200°C).

For the pastry cream: In a saucepan, heat the milk, salt, and vanilla sugar (or vanilla extract).

While the milk is heating, in a large bowl, beat the sugar and eggs with a wooden spoon until the mixture is pale. Stir in the flour, then gradually add the hot milk.